Self split push pull el84
- allesz
- Cap Cooler
Hallo mates, it's been a wile since I posted something new: as you can see my latest efforts have been in the tube amp fields, rather in stompboxes.
This is a self split push pull I build following some treads on tdpri.com (and also from the info I got on ax84.com) about the magnatone melodier 109 (wich used 6V6 power tubes btw).
The sound is really sweet: some people says this kind of output retains some of the richness of single ended amps, and I think they are right. For loud and clean chords a regular push pull (maybe fixed bias) amp is probably better and more powerfull, but with single notes, crunchy or full out distorted, the richness of the sound is great: it really sings.
I don't have the money and parts right now (and I don't really need so much power) but I suspect that an amp with a couple of EL34 or 6L6 would be just great in terms of power and tone.
The schematic is just a magnatone modified one; I omitted the diode bridge rectifier.
This is a self split push pull I build following some treads on tdpri.com (and also from the info I got on ax84.com) about the magnatone melodier 109 (wich used 6V6 power tubes btw).
The sound is really sweet: some people says this kind of output retains some of the richness of single ended amps, and I think they are right. For loud and clean chords a regular push pull (maybe fixed bias) amp is probably better and more powerfull, but with single notes, crunchy or full out distorted, the richness of the sound is great: it really sings.
I don't have the money and parts right now (and I don't really need so much power) but I suspect that an amp with a couple of EL34 or 6L6 would be just great in terms of power and tone.
The schematic is just a magnatone modified one; I omitted the diode bridge rectifier.
- allesz
- Cap Cooler
A small update after some rehearsals and live testing: I swapped the 10uF cathode bypass cap on the second triode with a 100nF one, the sound was too farty in the low end.
Sunday I had a rehearsal with my band, and I plugged the amp in a 2x12 cab with two celestion vintage 30 (great speakers me think), the sound was really good and the volume was right in a big band (drums, bass, sax and a keyboard player); it only started to crunch at 4 on the volume pot; so today I substituted the two 470K resistors on the power tubes grid with a couple of 220K (a popular mod on the 18 watt marshall clones) in order to get a little more clean headroom. I will test this mod soon at high volumes, at home the amp sounds just the same, but I can open it only to 1 or two before it gets annoying.
Another mod to increase the clean headroom would be to remove one (or both) cathode bypass caps; I am reluctant to do this because: a) I really like the tone right now. b) it seems that those caps are good in order to cut hum and noise (never expected this ). Maybe I can use a smaller cap on V1, but this will change the tone of the amp, or not?
Sunday I had a rehearsal with my band, and I plugged the amp in a 2x12 cab with two celestion vintage 30 (great speakers me think), the sound was really good and the volume was right in a big band (drums, bass, sax and a keyboard player); it only started to crunch at 4 on the volume pot; so today I substituted the two 470K resistors on the power tubes grid with a couple of 220K (a popular mod on the 18 watt marshall clones) in order to get a little more clean headroom. I will test this mod soon at high volumes, at home the amp sounds just the same, but I can open it only to 1 or two before it gets annoying.
Another mod to increase the clean headroom would be to remove one (or both) cathode bypass caps; I am reluctant to do this because: a) I really like the tone right now. b) it seems that those caps are good in order to cut hum and noise (never expected this ). Maybe I can use a smaller cap on V1, but this will change the tone of the amp, or not?
- allesz
- Cap Cooler
The last mod I swear!
I modded the tone control to get more clean headrom and tonal range; it's a BMP tone control as you can see. I tweaked it a little by ear and by the duncan tone calculator. Really happy of the tones I get.
The amp now is a lot cleaner, it starts to distort at seven on the volume pot. Tested it at a couple of gigs, both unmiked, with a 1x12 cab and a marshall 4x12 one. The results were really good and the volume was enough to keep up with bass, drums, another guitar player, sax and electric piano ; it was a small place btw.
I modded the tone control to get more clean headrom and tonal range; it's a BMP tone control as you can see. I tweaked it a little by ear and by the duncan tone calculator. Really happy of the tones I get.
The amp now is a lot cleaner, it starts to distort at seven on the volume pot. Tested it at a couple of gigs, both unmiked, with a 1x12 cab and a marshall 4x12 one. The results were really good and the volume was enough to keep up with bass, drums, another guitar player, sax and electric piano ; it was a small place btw.
- allesz
- Cap Cooler
It's really nice sounding.
After you try it you will find LTP quite stiff in comparison: this amp was a rebuiild of a cathode biased LTP amp.
I also have a stock jet city jca20H (LTP, fixed bias, cathode follower before tone controls, master volume, positive feedback... a very different amp) and it's a lot louder than this one (even the cleans are quite loud with my stock telecaster); but I think this is due to fixed bias: the LTP cathode biased amp (a fame tonmeister btw) was not much louder (if any) from this.
After you try it you will find LTP quite stiff in comparison: this amp was a rebuiild of a cathode biased LTP amp.
I also have a stock jet city jca20H (LTP, fixed bias, cathode follower before tone controls, master volume, positive feedback... a very different amp) and it's a lot louder than this one (even the cleans are quite loud with my stock telecaster); but I think this is due to fixed bias: the LTP cathode biased amp (a fame tonmeister btw) was not much louder (if any) from this.
- allesz
- Cap Cooler
This amp sounds very good and I use it for almost all the rehearsals and (few) gigs I did. I also have some lower and higher power options (vht sp6 and jet cith 20 head), but I use them sparingly right now; and I am building the board for an incoming 6L6 version right now. It will take months.
Wile building I had an idea to fight some hum/ripple from the circuit (not that I find the noise too much, but of course keeping it as low as possible can be triky with this phase splitting topology): put an electrolitic cap to ground where the two 4,7 K resistors in series, the ones that feed the screens of the pentodes, meets. You have just added another filtering stage (I used a 22uF - 450V cap), and the noise has gone down quite a bit.
Wile building the new board I have a big question about the value of those two screen grid resistors: the magnatone uses only one 4,7K resistor, with 6V6; I used two 4,7K resistors with the el84.... will this value will be good even for the 6L6?
btw I plan to put a small grid stopper in front of the second triode, and decrease (probably at 1,5K) the grid stoppers on the pentodes. The rest of the preamp will stay the same; even that probably the voltage going to the plates of the triodes will be higher...
Wile building I had an idea to fight some hum/ripple from the circuit (not that I find the noise too much, but of course keeping it as low as possible can be triky with this phase splitting topology): put an electrolitic cap to ground where the two 4,7 K resistors in series, the ones that feed the screens of the pentodes, meets. You have just added another filtering stage (I used a 22uF - 450V cap), and the noise has gone down quite a bit.
Wile building the new board I have a big question about the value of those two screen grid resistors: the magnatone uses only one 4,7K resistor, with 6V6; I used two 4,7K resistors with the el84.... will this value will be good even for the 6L6?
btw I plan to put a small grid stopper in front of the second triode, and decrease (probably at 1,5K) the grid stoppers on the pentodes. The rest of the preamp will stay the same; even that probably the voltage going to the plates of the triodes will be higher...
- clintrubber
- Breadboard Brother
Information
Nice thread & thanks for sharing those experiences! No idea how those items you mention w.r.t. the 6L6 would turn out, more pondering/experimenting...
Thanks
So the Fame Tonmeister amp was the donor for the Self split push pull amp ? As in: using PT & OT from the Fame ?allesz wrote:It's really nice sounding.
After you try it you will find LTP quite stiff in comparison: this amp was a rebuiild of a cathode biased LTP amp.
I also have a stock jet city jca20H (LTP, fixed bias, cathode follower before tone controls, master volume, positive feedback... a very different amp) and it's a lot louder than this one (even the cleans are quite loud with my stock telecaster); but I think this is due to fixed bias: the LTP cathode biased amp (a fame tonmeister btw) was not much louder (if any) from this.
Thanks
- allesz
- Cap Cooler
Yes, I recycled everithing I could.
It was not bad, but I wanted to build something new.
No regrets, but I am lusting over a 25/30 2x6L6 version.... I may rebuild again the tonemeister, but I fear regrets and, mostly, I wonder if bigger transformers will fit
It was not bad, but I wanted to build something new.
No regrets, but I am lusting over a 25/30 2x6L6 version.... I may rebuild again the tonemeister, but I fear regrets and, mostly, I wonder if bigger transformers will fit
- clintrubber
- Breadboard Brother
Information
Hadn't heard of the Tonmeister before, but I like the idea of it. Saw some pics. Can well imagine larger iron wouldn't fit, and the tube-compartiment looked small, so even if the iron wiuld fit, would those larger 6L6 tubes do ?
I figure you've also considered a quad of EL84 ? (but would still require larger iron)
Curious to your 6L6 experiments, please keep us posted.
Thanks
I figure you've also considered a quad of EL84 ? (but would still require larger iron)
Curious to your 6L6 experiments, please keep us posted.
Thanks